Martian Canali

Viking Lander

Labeled release experiment (LR)

Moistened soil sample with a liquid nutrient medium that contained carbon-14.

Container monitored to see if carbon-14 released into air.

Control samples

Martian soil samples were heated to 160 C, a temperature that destroyed all biological activity in terrestrial soils before testing, and then tested with the same three experiments.

Life on Mars?

Molecular analysis Experiment

Heated soil to look for organic molecules.

Found a complete absence of any organic molecules in the Martian soil.

The Conclusion

The Martian surface is completely devoid of life.

Gas release was due entirely to chemistry.

High concentrations of chemicals such as hydrogen peroxide and strong ultraviolet radiation combine to make the surface of Mars completely sterile.

Inconclusive?

These three experiments have been shown since the seventies to miss life present in arid regions on Earth.

Assumed, incorrectly, that all life got energy either from photosynthesis or by eating organic compounds.

Fossilized bacteria?

Beagle 2

Landed on Mars Christmas day 2003

Contained a mass spectrometer 100 times more sensitive than Vikings’ to look for organic molecules and peroxides in soil

Test for carbon-12 to carbon-13 ratio

Mars Rover

Grey Hematite

Opportunity landing site

Curiosity

Gale crater Curiosity landing site

Gale Crater

The Face on Mars

Exam 2 Tuesday

Covers Chapters 7-10, & 14

One sheet of notes with writing on one side only

Jovian Planets

Discussion

Why do you think it is that of the Jovian planets we know the most about Jupiter?

Discussion

Jupiter is 71% hydrogen, 24% helium, and 5% heavier elements. How can we figure out the composition of Jupiter?

Discussion

Jupiter has more heavy elements than the Sun does. If both formed from the same nebula, why do you think that is?

Jupiter: 71% hydrogen, 24% helium, 5% heavier elementsSun: 73.4% hydrogen, 25% helium, 1.6% heaver elements

Discussion

Jupiter is 3 times as massive as Saturn, yet is only 1.2 times bigger. Why do you think that is?

Mass-radius relation

Discussion

All the Jovian planets are covered with thick clouds. How do you know anything at all about the interior of the Jovian planets if we cannot obverse them?

Clues to internal structure

1. Mean density

2. Gravitational mapping

3. Shape of the planet

Mean density of planets

Earth 5.5 g/cm3

Mercury 5.4 g/cm3

Venus 5.2 g/cm3

Mars 3.9 g/cm3

Moon 3.4 g/cm3

Neptune 1.6 g/cm3

Sun 1.4 g/cm3

Jupiter 1.3 g/cm3

Uranus 1.3 g/cm3

Saturn 0.7 g/cm3

Rotation

The Jovian planets tend to spin very fast

Jupiter – 9 h 55 m 29 sSaturn – 10 h 39 m 25 sUranus – 17 h 14 m 24 sNeptune – 16 h 6 m 36 s

Discussion

What happens as the rotation rate of a planet is increased?

Oblateness

Jupiter’s oblateness

Equatorial radius: 71,492 km

Polar radius: 66,854 km or 6.5% smaller.

Oblateness 6.5

Discussion

How does the oblateness of a planet depend on the rotation rate, the size, and the mass of a planet?

Discussion

Saturn’s diameter at its equator is 10% larger than its pole to pole diameter.

Saturn is smaller than Jupiter and rotates more slowly. How come its equatorial bulge is bigger?

Saturn’s internal structure

For Saturn’s size and density, it is not oblate enough to have the same internal structure as Jupiter.

Saturn has a larger rocky core, comprising about 10% of its total mass (about 9.5 Earth masses).

Discussion

Why is Saturn’s liquid metallic hydrogen layer so much smaller than Jupiter’s?

Discussion

The equators rotate faster than the poles. The poles on Jupiter take and extra 5 minutes to complete a rotation.

With differential rotation and a big liquid metallic interior, what do you expect to be the result?

Jupiter’s magnetic field

Discussion

If Jupiter and Saturn rotate differentially, how do we decide what their rotation rates are?

Discussion

Saturn’s magnetosphere is not as big as Jupiter’s, between 10 to 20 % that of Jupiter. Why not?

Discussion

Unlike the terrestrial planets that receive most of their energy from the Sun, the planet Jupiter emits about twice as much energy as it receives from the Sun. Where do you think this energy comes from?

Jupiter as a failed star

Core at a pressure of 70 million atm Temperature 22,000 K

Jupiter would need 80 times its current mass to start hydrogen fusion in its core.

Jupiter’s atmosphere

Hydrogen 86.4% Helium 13.6%Water 0.1%Methane 0.21%Ammonia 0.07%

Discussion

Jupiter, like the Earth has a stratosphere. Why do you think that is?

Cloud bands

Why do you think Jupiter has cloud bands?

Discussion

The boundaries between the zones and belts on Jupiter mark a change in wind direction with typical speeds of 500 km/hr. What causes these strong eastward and westward winds on Jupiter?

Jupiter in the IR and visible

Discussion

What does the infrared picture of the bands tell you about the difference between the belts and zones of Jupiter?